q6voiced: use pcm_start instead of pcm_prepare

Some drivers do their init and deinit in prepare and shutdown callbacks. For these drivers this daemon worked already. However, the proper way is to use the trigger callback according to the ALSA documentation in the kernel [1]. Therefore, use pcm_start to trigger prepare, shutdown, and trigger callbacks.

[1] https://www.kernel.org/doc/html/latest/sound/kernel-api/alsa-driver-api.html#c.snd_compr_ops

CC: @joelselvaraj